Auxiliary switch with amplified contact-opening movement



Oct. 19, 1965 w. R. HARPER, JR 3,213,245

AUXILIARY SWITCH WITH AMPLIFIED CONTACT-OPENING MOVEMENT Filed 001;. 17. 1961 //v raw-0R,"

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3,213,245 AUXILIARY SWITCH WITH AMPLIFIED CONTACT-OPENING MOVEMENT Walter Reeve Harper, Jr., Barrington, R.I., assignor to Texas Instruments Incorporated, Dallas, Tex., a corporation of Delaware Filed Oct. 17, 1961, Ser. No. 145,582 Claims. (Cl. 200-113) This invention relates to condition-responsive devices, and with regard to certain more specific features, to thermal-ly responsive, electrical switches which are provided with auxiliary switching means.

Among the several objects of the present invention may be noted the provision of a thermally responsive switch particularly suited for protection of electrical motors and energy-translating devices, which switch includes an auxiliary switching means for controlling a pilot or auxiliary circuit; the provision of a thermally responsive switch operated by a snap-acting thermally responsive member which controls a primary circuit, and an auxiliary switching mechanism which is actuated in response to movement of the snap-acting member; the provision of devises of the class described, wherein the auxiliary switching mechanism does not interfere with the snap-acting motion or deleteriously affect calibration of the snapacting thermostatic member; the provision of devices of the class described, which provide amplified contact-opening movement for the auxiliary switching arrangement in response to relatively small actuating movement of the snapacting thermal element; the provision of devices of the class described, which provide for snap actuation of the auxiliary switching mechanism; and the provision of devices of the class described which are simple in construction, economical to assemble and manufacture, and which are dependable in operation.

Other objects will be in part apparent and in part pointed out hereinafter.

The invention accordingly comprises the elements and combinations of elements, features of construction, and arrangements of parts which will be exemplified in the structures hereinafter described, and the scope of the application of which will be indicated in the following claims.

In the accompanying drawings, in which one of the various possible embodiments of the invention is illustrated:

FIG. 1 is a vertical section, with some parts shown in full, of a condition-responsive device according to the present invention;

FIG. 2 is a section taken on line 22 of FIG. 1;

FIG. 3 is a fragmentary elevational view, similar to FIG. 1, indicating relative motion between parts; and

FIG. 4 is a perspective view of a motion-transfer member of the device shown in FIGS. l-3.

Similar reference characters indicate corresponding parts throughout the several views of the drawings.

Dimensions of certain of the parts as shown in the drawings have been modified for the purposes of clarity of illustration.

The present invention is applicable to situations where it is desired to control one or more devices in response to control or actuation of another device. The present invention is particularly useful for (though not limited to) electrical motor protection (to prevent excessive heating and damage of the motor windings) where it is desired to actuate or control a separate auxiliary or pilot circuit in response to energization or deenergization of the motor circuit.

The combined thermally responsive switch and auxiliary switch of the present invention is particularly useful, for example, with processing machinery which employs two or more motors, where if one motor is stopped by the nited States Patent 0 3,213,245 Patented Oct. 19, 1965 ice action of its motor protector, it is important to de-energize each of the other motors. An example of such a situation is in machine tool equipment where a coolant pump motor has been stopped by action of a motor protector due to excessive motor temperatures, and the remainder of the equipment motors (if not de-energized) would continue to perform their intended functions without the benefit of proper cooling of the cutting tool, and be exposed to undesirable damage. The switch, according to the present invention, advantageously solves these problems. Although the auxiliary switching mechanism of the present invention is particularly useful in such applications, it is also useful in other applications for signal purposes, such as operating an indicator lamp, buzzer, bell, or secondary function, such as a solenoid to actuate pneumatic, hydraulic or mechanical devices, etc.

Briefly, the invention involves an organization including a snap-acting, thermally responsive, circuit-controlling element, and an auxiliary switching contact arrangement mounted for actuation in response to snap movement of the thermal element. A movably mounted, auxiliary switching, contact-carrying arm is mounted adjacent one side of the snap-acting element with a motiontransfer means interposed therebetween for eifecting contact actuating movement in response to contact actuating snap movement of the thermal element. The auxiliary contact-carrying arm controls a set of contacts in a pilot or auxiliary circuit which is electrically isolated from the electrical circuit controlled directly by the snap-acting thermostatic element. The auxiliary contact switching arm and motion-transfer member are so arranged with respect to the snap-acting element so as not to interfere with snap action, or deleteriously affect the calibration of the snap-acting element, while providing for amplified auxiliary contact-opening motion.

Referring now more particularly to FIGS. 1-3 of the drawings, there is shown at a switch according to the present invention. Switch 10 includes a casing 12 formed of electrically insulating material, such as one of the moldable phenolic resins. Casing 12 is provided with a pair of open-ended slots 14 and 16, which cooperatively interfit with and respectively mount electrically conductive terminals 18 and 20. Terminals 18 and 20 respectively provide electrical contacts 22 and 24 at their upper surface, for engagement respectively with contacts 26 and 28 which are mounted on a composite snap-acting thermostatic plate member 30, as shown. Snap-acting element 30, is or may be, for example, a dished, bimetallic snap-acting thermostatic disc of the type shown and described in the Spencer Patent No. 1,448,240 or in the Vaughan et a1. Patent No. 2,317,831.

Casing 12 is provided with a threaded opening 32, in which is threaded a portion of an adjusting screw or mounting post 34. Threaded post member 34 provides a shoulder 36 and includes a reduced diameter portion 38, as best seen in FIGS. 1 and 3. Snap-acting element is provided with a centrally located aperture 40 (as best seen in FIGS. 1 and 3). Reduced diameter projecting portion 38 of post 34 is received within aperture 40, and projects beyond the other side of element 30, as shown, to mount element 30 thereon, as shown and described in the aforementioned patents. Shoulder 36 is disposed for supportive engagement with element 30, when the latter is in the FIG. 3 position.

Switch 10 includes a support member 50, formed of electrically insulating material. Support member is a fiat, disc-shaped member and is provided with a centrally located open-ended aperture 52. The free end of projecting portion 38 is provided with a reduced diameter portion 54 which provides a supporting shoulder 56 for member 50, as shown. Reduced diameter portion 54 is received within aperture 52, and projects beyond support member 50. Support member 50 is fixed to projecting portion 38 by upsetting the free end of reduced diameter portion 54, as at 58, to provide a rivet-like construction. A washer or retainer member 60 is interposed between upset portion 58 and support 50, as shown. Support member 50, as thus mounted, abuts against shoulder 56 and is tightly fixed to post 34, and is also preferably (though not necessarily) prevented from rotating relative thereto. Support member 50 will rot-ate with threaded mounting post 34, when the latter is rotated to effect adjustment and calibration of the snapacting element 30.

Support member 50 mounts a fixed or stationary elec trical contact 62, as shown. Electrical contact 62 is carried by a terminal member 64, which is riveted and fixed to support member 50, as at 66. Terminal member 64 includes a bent portion 68 which extends exteriorly of switch through a suitable aperture provided in a cover member 70, as shown.

Switch 10 further includes an auxiliary, contact-carrying movably mounted member generally referred to by numeral 72, formed of suitable electrically conductive material, such as for example, beryllium copper. Member 72 includes an offset tab portion 76 interconnected with an elongated, contact-carrying arm portion 74 by a resilient spring portion 78, as shown. Offset tab portion 76 is mounted on and fixed to support member 50, for example, by means of a rivet 80, thereby cantilever mounting the auxiliary switch member 72, as shown. Portions 74, 76 and 78 may be formed integrally, as shown. Electrically connected (or integrally formed with) offset tab portion 76 is a terminal portion 82 which projects exteriorly of switch 10, through a suitable opening in cover member 70, as suggested in dashed lines in FIGS. 1 and 3 for electrical connection to an external circuit.

Elongated arm 74 is electrically connected to and carries an electrical contact 84 adjacent its free end for movement into and out of engagement with fixed contact 62 in response to movement of arm 74. Elongated portion 74 is stiffened along a substantial or major poriton of its length by upstanding rib stiffening members 86 and 88, which may be formed integrally with arm 74, as shown. The stiffening of elongated member 74 causes the latter to function as a lever to provide snapaction actuation of contacts 62 and 84, and amplified contacts-opening motion, in response to snap action of thermally response element 30, as will be more clear from the ensuing description.

Switch 10 also includes a motion-transfer member formed of a suitable electrically insulating material, generally referred to by numeral 100, as best seen in perspective in FIG. 4. Motion-transfer member 100 includes a shank portion 102 which preferably has a polygonal or rectangular cross-sectional shape, as shown. Member 100 further includes a circumferentially extending flange portion 104. Flange portion 104 is tapered, as at 106, to provide a reduced cross-sectional area surface portion 108, which engages and abuts a centrally located portion of disc circumferentially adjacent mounting aperture 40, as best seen in FIGS. 1 and 3. The relatively small contact area of surface 108 co-operates with the central portion of disc 30 to obviate, or at least minimize, any interference with snap action and calibration of the snap-acting disc 30. Member 100 further includes a pair of radially projecting arcuateshaped boss portions 110 and 112, as best seen in FIG. 4, and is provided with a centrally located open-ended aperture 114, as best seen in FIGS. 1 and 3. Motiontransfer member 100 is slidably mounted on portion 38 of mounting post 34, portion 38 being received within open-ended aperture 114. As clearly shown in FIGS. 1 and 3, shank portion 102 is received within a complementary shaped aperture 115, provided in elongated contact arm 74. Motion-transfer member 100 is thus slidably mounted on post 34 with respect to member 72, supporting member 50 and element 30. As clearly shown in FIGS. 1 and 3, flange 104 is disposed intermediate snap-acting disc 30 and elongated arm 74, with arcuateshaped, radially projecting bosses 110 and 112 disposed for engagement with arm 74. Arcuate shaped bosses 110 and 112 advantageously provide for line contact with arm 74 to obviate, or at least minimize, any tendency for binding between relative movable parts, such as sliding movement of member on projecting portion 38.

It will be noted from inspection of FIGS. 1 and 3, that elongated arm 74 is engaged by the arcuate bosses and 112, at a portion thereof which is remote from the free end thereof, and provides motion multiplied or amplified contacts 62, 84- opening movement, in response to the very limited and relatively small arm 74 actuating snap movement of the snap-acting disc 30 at its center. Resilient spring portion 78, which interconnects offset tab portion 76 and arm 74, urges contact arm 74 for movement downwardly, toward element 30, as seen in FIG. 3, in a contacts 62, 84 opening direction. Resilient spring portion 78 urges arm 74 into engagement with member 100, and biases member 100 into engagement with snap element 30.

In practice, mounting post 34, element 30 with contacts 26 and 28 mounted thereon, follower or motiontransfer member 100, support member 50, with contact 62, terminal 64, terminal 82 and movably mounted switch arm member 72 secured thereto, will be assembled together to form a subassembly unit. Thereafter, all that is necessary to complete the switch 10 is to mount this subassembly 0n the casing 12 by threadedly engaging mounting post 34 within threaded aperture 32. Post 34 will then be rotated to properly calibrate snapacting element 30, all as described in the aforementioned patent. Thereafter, a nut 34a is applied about the free extending end of threaded post 34, to maintain the parts in final, assembled, calibrated relation.

It will be clear that when the post 34 is rotated to calibrate the snap-acting element 30, surface 108 of motion-transfer member 100 will bear against the upper surface of the snap-acting member 30 (when the latter is in the position as shown in FIG. 1) to provide desired calibration. The height of shank portion 102 is selected so as to provide the necessary relationships between parts to provide for desired operation, and so that shank 102 will engage the underside of support member 50, whereby surface 108 will present a fixed surface for bearing against the snap-acting element 30 during calibration when screw 34 is rotated.

The end 74a of contact arm 74, adjacent the stiffening ribs, can also be bent for calibrating the auxiliary switching mechanism by moving contact 84 relative to contact 62, either to increase or diminish relative contact pressure therebetween. Calibration of arm 74 may take place prior to insertion of the subassembly Within casing 12.

The polygonal shaped or rectangular shaped crosssectional configuration of shank portion 102 co-operates with the complementary shaped aperture 115 provided in arm 74 of the switch member 72 to prevent relative rotation between parts. The relatively stiff and rigid nature of arm 74 causes it to move as a lever, and to provide maximum contact motion for movable contact 84. After the parts have been assembled in the manner described above, cover member '70 is inserted in a complementary shaped recess with terminal portions 68 and 82 extending therefrom. Cover member '70 is formed of electrically insulating material, and may be fastened to casing 12 in any known, convenient manner.

Switch 10 thus provides control for two electrically isolated circuits. Terminals 18 and 20 may be connected in a primary circuit (e.g. as in a motor protector circuit), the primary circuit through the switch being as follows: from terminal 18 to contact 22, to contact 26, serially through snap-acting thermal element 30, to contact 28, to contact 24, then to terminal 20. The auxiliary switching mechanism can be connected in a secondary or pilot circuit (e.g. to control a series of motors, as in the machine tool equipment example described above), the circuit being through terminal portion 82, to offset tab portion 76, through spring portion 78, through arm 74, to contact 84, to contact 62, to terminal 64, and projecting terminal portion 68, when the parts are in the FIG. 1 condition.

Snap-acting element 30, when it reaches a predetermined temperature level in response to ambient heat and/ or heat generated internally by the current traversing it, will snap from the FIG. 1 position to the FIG. 2 position, and separate contacts 22, 26 and 24, 28 to open the primary circuit. Element 30, in snapping from the FIG. 1 to the FIG. 3 condition, permits motion-transfer or follower member 100 to move downwardly under the spring bias exerted by spring portion 78 through arm 74 to quickly open contacts 62 and 84. It can thus 'be said that contacts 62 and 84 also open with snap action.

It will be seen that'the center portion of element 30 engaged by surface 108 of member 100, moves downwardly only a relatively small amount, when element 30 snaps from the FIG. 1 to the FIG. 3 condition, its downward movement being limited by engagement with shoulder or flange 36. The motion-transfer member 100, and the portion of arm 74 with which its has line contact, also move downwardly by this small amount. However, because of the motion am-pi-lfying lever arrangement described above, this relatively small actuating movement is advantageously utilized to provide considerably amplified contacts 62, 84 opening move ment.

It will be clear that snap'acting element 30, when in the FIG. 3 hot condition, upon cooling sufficiently, will snap back to the FIG. 1 contacts 22, 26 and 24, 28 closed configuration, moving the center portion of element 30 upwardly against motion-transfer member 100 and arm 74 to quickly close contacts 62 and 84 against the bias exerted by spring portion 78. It will thus be seen that contacts 22, 26; 24, 28 and 62, 84 are snap actuated substantially simultaneously by snap action of element 30.

From the above, it can be seen that the construction according to the present invention, advantageously utilizes very limited center motion of the snap-acting element, which is amplified to provide desirable large contact-opening distances for the auxiliary contacts, while obviating or at least minimizing interference with the snap-acting operation and calibration of the thermally responsive element 30.

Although the switch embodiment, as described and illustrated in the drawings, is primarily useful for singlephase type motors, it will be understood that the invention can also be applied to three-phase type motors. It will be understood that the combined snap-acting and auxiliary switching mechanisms, although described and illustrated as operating electrical contacts for circuit controls, can also be utilized to control pilot circuit components for a secondary function, such as for example, a pilot light, solenoid valve, a pneumatic or mechanical operating device, etc.

As many changes could be made in the above constructions without departing from the scope of the invention, it is intended that all matter contained in the above description or shown in the accompanying drawings, shall be interpreted as illustrative and not in a limiting sense, and it is also intended that the appended claims shall cover all such equivalent variations as come within the true spirit and scope of the invention.

I claim:

1. An electrical switch comprising an electrically insulating base; a thermally responsive, snap-acting element;

a post member threadedly engaged with said insulating base mounting said snap-acting element on said base; said post member including a portion received in and extending through a centrally located aperture provided on said snap-acting element; a first electrical contact mounted on said base; said snap-acting element mounting and electrically connected to a movable contact which is movable into and out of engagement with said first contact in response to snap movement of said snap-acting element at predetermined conditions; an electrically insulating sup port member mounted on said portion of said post; a stationary contact mounted on said support member; a movable member carried by said support; said movable member mounting a movable contact for movement into and out of engagement with said stationary contact in response to movement of said movable member; an electrically insulating motion-transfer member slidably supported on said portion of said post and positioned intermediate said movable member and said snap-acting element and positioned to engage said movable member in such a manner that motion transferred from said motiontransfer member to said movable contact mounted on said movable member is amplified, to effect contact actuating movement of said movable member in response to snap action of said thermally responsive element; and spring means urging said movable member for movement in a direction toward said snap-acting element.

2. The electrical switch as set forth in claim 1 and wherein said movable member includes an offset tab portion adjacent one end thereof and an elongated, contact-carrying arm which is stiffened along a major portion of its length against bending; said spring means interconnecting said offset tab portion with said elongated, contact-carrying arm; said last-named movable contact being mounted adjacent the free end of said elongated, contactcarrying arm; said offset tab portion being secured to said support member and cantilever mounting said movable member; said arm being positioned with respect to said motion-transfer member for engagement therewith at a portion of said arm which is closer to said offset tab portion than to said free end.

3. An electrical switch comprising an electrically insulating base; a pair of spaced electrical terminal members mounted on said base; each of said terminal members providing an electrical contact; a post member mounted on and threadedly engaged with said base member; a thermally responsive, snap-acting element mounted on said post member; said post member including a portion received in and extending through a centrally located aperture provided in said thermally responsive element; said element including a pair of spaced electrical contacts mounted thereon and positioned for mating engagement with said first-named pair of electrical contacts; a support member mounted and fixed to said portion of said post member; a second pair of electrical terminals mounted on said support member; one of said electrical terminals providing a stationary electrical contact; an electrically conductive, contact-carrying member electrically connected to the other of said second pair of electrical terminals; said contact-carrying member including an offset tab portion connected to said support member cantilever mounting said contact-carrying member; said contactcarrying member including an elongated arm carrying an electrical contact adjacent the free end thereof for movement into and out of engagement with said stationary contact; said contact-carrying member including a resilient sprm g portion interconnecting said olfset portion and said elongated arm, and urging said elongated arm for movement in a direction toward said snap-acting element; an electrically insulating motion-transfer member slidably mounted on said portion of said post intermediate said support and said snapacting element; said motion-transfer member including a portion positioned intermediate the ends of and engageable with said elongated arm at a portion of said arm which is closer to said offset tab portion than to said free end, and with said snap-acting element, whereby the motion of the said transfer member is amplified at the said free end of the said contact-carrying member.

4. The switch as set forth in claim 3 and wherein said motion-transfer member includes a shank portion; said portion of said motion-transfer member intermediate said elongated arm and snap-acting element comprising a peripherally extending flange having a pair of spaced, arcuate-shape bosses positioned for engagement with said elongated arm.

5. The switch as set forth in claim 4 wherein said motion-transfer member is provided with an aperture in which the said post member is slidably received and wherein said shank portion of said motion-transfer member has a substantially rectangular cross-sectional configuration, and is slidably received within a complementary shaped aperture provided in an elongated arm of said contact-carrying member.

References Cited by the Examiner UNITED STATES PATENTS 1,655,967 1/28 Matthews 20()-122 2,501,155 3/50 Bolesky 200122 X 2,694,121 11/54 Vander Pyl 20()1 13 2,810,041 10/57 Wills 200-113 2,839,637 6/58 Epstein 200113 FOREIGN PATENTS 1,271,187 7/61 France.

BERNARD A. GILHEANY, Primary Examiner.

ROBERT K. SCHAEFER, Examiner. 

1. AN ELECTRICAL SWITCH COMPRISING AN ELECTRICALLY INSULATING BASE; A THERMALLY RESPONSIVE, SNAP-ACTING ELEMENT; A POST MEMBER THREADEDLY ENGAGED WITH SAID BASE; BASE MOUNTING SAID SNAP-ACTING ELEMENT ON SAID BASE; SAID POST MEMBER INCLUDING A PORTION RECEIVED IN AND EXTENDING THROUGH A CENTRTALLY LOCATED APERTURE PROVIDED ON SAID SNAP-ACTING ELEMENT; A FIRST ELECTRICAL CONTACT MOUNTED ON SAID BASE; SAID SNAP-ACTING ELEMENT MOUNTING AND ELECTRICALLY CONNECTED TO A MOVABLE CONTACT WHICH IS MOVABLE INTO AND OUT OF ENGAGEMENT WITH SAID FIRST CONTACT IN RESPONSE TO SNAP MOVEMENT OF SAID SNAP-ACTING ELEMENT AT PREDETERMINED CONDITIONS; AN ELECTRICALLY INSULATING SUPPORT MEMBER MOUNTED ON SAID PORTION OF SAID POST; A STATIONARY CONTACT MOUNTED ON SAID SUPPORT MEMBER; A MOVABLY MEMBER CARRIEDBY SAID SUPPORT; SAID MOVABLE MEMBER MOUNTING A MOVABLE CONTACT FOR MOVEMENT INTO AND OUT OF ENGAGEMENT WITH SAID STATIONARY CONTACT IN RESPONSE TO MOVEMENT OF SAID MOVABLE MEMBER; AN ELECTRICALLY INSULATING MOTION-TRANSFER MEMBER SLIDABLY SUPPORTED ON SAID PORTION OF SAID POST AND POSITIONED INTERMEDIATE SAID MOVABLE MEMBER AND SAID SNAP-ACTING ELEMENT AND POSITIONED TO ENGAGE SAID MOVABLE MEMBER IN SUCH A MANNER THAT MOTION TRANSFERRED FROM SAID MOTIONTRANSFER MEMBER TO SAID MOVABLE CONTACT MOUNTED ON SAID MOVABLE MEMBER IS AMPLIFIED, TO EFFECT CONTACT ACTUATING MOVEMENT OF SAID MOVABLE MEMBER IN RESPONSE TO SNAP ACTION OF SAID THERMALLY RESPONSIVE ELEMENT; AND SPRING MEANS URGING SAID MOVABLE MEMBER FOR MOVEMENT IN A DIRECTION TOWARD SAID SNAP-ACTING ELEMENT. 